1. Field of the Invention
The present invention relates to seals for use in subsea applications. More particularly, the present invention the relates to metal-to-metal seals that are applied of the junctions between coupling elements or hubs in subsea application. Additionally, the present invention relates to seals that have multiple pressure-retaining contact points between outer surface of the seal and the inner surface of the coupling elements.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Metal-to-metal sealing is commonly used in subsea hydrocarbon production assemblies. For example, subsea wells typically have a subsea wellhead assembly at the seafloor with a subsea production tree mounted on the wellhead assembly. The tree has valves connected to flow lines for controlling the flow from the well. In another type of installation, a string of tieback conduits extend from the subsea wellhead assembly to a platform at the surface. A surface tree is mounted on the upper end of the tieback conduit. Some riser systems have inner and outer tieback conduits, each of which is run separately and connected by a tieback connector. The inner and outer tieback conduits make up the tieback riser in that type of system.
In each of these subsea connections, there is employed a first coupling element and a second coupling element. Typically, these coupling elements are referred to as “hubs”. The hubs are joined together with the seal positioned at the interface of the hub so as to establish a strong liquid-tight connection therebetween. The seal is preferably a metal-to-metal seal such that it seals to an internal component of the subsea wellhead housing assembly. Metal-to-metal seals have a variety of configurations.
Elastomeric seals have been commonly used in the past. These elastomeric seals have certain disadvantages. In particular, these elastomeric seals have the inability to withstand the deteriorating effects of the subsea environment for extended periods of time. Additionally, the elastomeric seals tend to be unable to contain the higher pressures imposed on such hydraulic systems.
In the past, such metal seals have usually had a single pressure contact point with a surface of the first coupling element and a single surface contact point with another surface of the second coupling element. As a result, if this pressure contact point is parted under pressure, the seal will generally blowout and be lost. As such, each of these metal-to-metal seals has the inability to establish a back-up type of pressure connection whereby if a single seal contact point with a surface of the coupling element is lost, there remains a secondary pressure contact point within the coupling element. Additionally, such metal-to-metal seals can deform under the pressures applied thereto. When sufficient deformation occurs, the sealing relationship can be lost and leaks can occur. As such, there is a need to provide a metal-to-metal seal for subsea application which avoids the possibility of deformation and the resulting leakage and pressure loss.
In the past, various patents have issued relating to such metal-to-metal seals and relating to subsea coupling sealing connections. For example, U.S. Pat. No. 4,884,584, issued on Dec. 5, 1989 to R. E. Smith, describes a coupling having a metal-to-metal seal formed between a male member and a female member. The seal is pre-loaded by means of an internal preload mechanism. The male member engages the seal member so as to form the sealing relation between the two. The seal members are allowed to float, or slide, longitudinally within the bore of the female coupling member between an extended position and a compressed position. The seal member is biased by the preload mechanism into the extended position.
U.S. Pat. No. 5,385,169, issued on Jan. 31, 1995 to O. D. Odelius, describes a subsea fluid coupling employing metal-to-metal sealing. The subsea fluid coupling includes male and female parts which can be quickly connected and disconnected. The metal seals are carried by the female and male parts and engage planar metal surfaces to produce metal-to-metal sealing around the first and second passages when the coupling is connected or disconnected. Holes extend laterally through the gate and the conduit body, respectively, for creating a lateral pressure balance on the gate and conduit body.
U.S. Pat. No. 5,839,765, issued on Nov. 24, 1998 to Carter et al., discloses a metal seal ring for a tubular joint. The tubular joint has end hubs in opposed relationship and secured by a clamp. A primary seal ring has external tapered sealing surfaces engaging internal tapered sealing surfaces on the hubs to provide a primary seal. Secondary sealing surfaces on the hubs are engaged by O-rings to seal against external fluid flow to the seal ring. O-rings permit internal fluid flow outwardly from the seal ring.
U.S. Pat. No. 6,722,426, issued on Apr. 20, 2004 to Sweeney et al., teaches a gasket with multiple sealing surfaces. This gasket is a metal seal for a wellhead assembly that has upper and lower legs extending in opposite directions from each other and a rib extending radially outward from a junction of the legs. A first conical band on the upper leg extends uninterrupted from the rib a selected distance toward a tip of the upper leg. A second conical band on the upper leg extends uninterrupted from the tip of the upper leg toward the first conical band. An annular recess is located between the first and second conical bands.
U.S. Pat. No. 7,467,799, issued on Dec. 23, 2008 to O. D. Tarlton, provides a composite metal-to-metal seal having a core of relatively soft metal and an annular region of relatively soft metal. The seal is a ring having a pair of annular regions which provide tapered annular sealing surfaces for engaging respective sealing surfaces of mating hubs.
U.S. Pat. No. 7,819,439, issued on Oct. 26, 2010 to Paton et al., shows a fishtail bore seal. This bore seal serves to connect oil and gas tubular members. The bore seal has a fishtail profile which facilitates the use of resilient seals to provide resistance to external pressures in addition to the traditional metal-to-metal seal between the bore seal and the tubular members. A pressure relief valve is disposed within the bore seal to verify the integrity of the metal-to-metal seal with respect to internal bore pressure.
U.S. Pat. No. 8,096,560, issued on Jan. 17, 2012 to Pallini, Jr. et al., provides a metal-to-metal seal for a smooth bore for sealing contact with an opposing surfaces. The seal assembly includes an annular seal body with a sealing surface on one side of the seal body. An end of the sealing surface includes a sealing face for sealing contact with the opposing surface. The sealing surface also includes at least one support point that contacts the opposing surface when the seal is placed in sealing contact.
U.S. Pat. No. 8,226,089, issued on Jul. 24, 2012 to Pallini, Jr. et al., provides a seal assembly includes a tubular member having a longitudinal axis and a tubular member seal profile. A metal seal ring has a proximal base and a distal end that has a seal ring seal profile between the proximal base and distal end so as to contact the seal profile of the tubular member. A distal annular recess is in one of the seal profiles. The distal annular recess is spaced axially from the distal end of the seal ring so as to define a seal surface between the distal end of the seal ring and the distal annular recess that engages a seal surface of the seal profile of the tubular member. A proximal annular recess in one of the seal profiles is spaced axially from the distal annular recess so as to define a support area axially spaced from the metal-to-metal seal area.
European Patent No. 1373766, published on Jan. 2, 2004 to C. N. Crawford, describes an annular metal-to-metal sealing system which has a metal member defining an annular internal or external sealing surface. The annular seal body is composed of a high-strength metal material which is positioned in concentric relationship with the annular sealing surface and is sufficiently flexible to become spring-loaded during assembly. The annular seal body defines one or more annular seal retainer grooves each having an annular soft metal sealing inset therein with a portion thereof exposed for sealing engagement with the annular sealing surface. The spring-loaded characteristic of the annular seal body applies constant force to maintain the soft metal seal insert constantly energized sealing relation with the annular sealing surface.
U.S. Patent Publication No. 2004/0056432, published on Mar. 25, 2004 to Walker et al., provides a composite metal sealing ring for sealing between tubular members. Each of the tubular members has first and second conical inner sealing surfaces. A metal sealing ring has corrosion-resistant inlays defining opposing conical outer sealing surfaces for sealing with the first and second conical inner sealing surfaces.
U.S. Patent Publication No. 2007/0013146, published on Jan. 18, 2007 to J. A. Gariepy, shows a sealing ring for providing for sealing between truncated conical surfaces of adjoining members. The sealing ring includes an annular metal seal body having first and second truncated conical surfaces each for planar engagement with a truncated conical surface on a respective member. The annular sealing ring insert has a radially inward recess in the respective truncated conical body.
It is an object of the present invention to provide a subsea seal assembly that has dual seal points on each coupling element.
It is another object of the present invention to provide a subsea seal assembly that has high capacity and load compression.
It is another object of the present invention to provide a subsea seal assembly which provides a metal-to-metal seal.
It is still another object of the present invention to provide a subsea seal assembly that allows for the determination of the efficacy of the seal before pressurization.
It is another object of the present invention to provide a subsea seal assembly that allows for the subsea testing of the connection.
It is still a further object of the present invention to provide a subsea seal assembly that effectively maintains the seal in the event of failure of a portion of the seal assembly.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.